Method of condensing metallic vapors carried in a stream of gas



Oct. 9, 1956 H. K. NAJARIAN 2,756,114

METHOD OF CONDENSING METALLIC VAPOR-S CARRIED IN A STREAM OF GASOriginal Filed March 15, 1952 4 Sheets-Sheet 1 INVENTOR HERAND K.NAJARIAN BY Z/M 7M ATTORNEY Oct. 9, 1956 H. K. NAJARIAN METHOD OFCONDENSING METALLIC VAPORS CARRIED IN A STREAM OF GAS 4 Sheets-Sheet 2Original Filed March 15, 1952 INVENTOR ATTORNEY Oct. 9, 1956 H. K.NAJARIAN METHOD OF CONDENSING METALLIC VAPORS CARRIED IN A STREAOriginal Filed Marqh 15, 1952 [NIH M OF GAS 4 Sheets-Sheet 3 INVENTOR,1? HERAND K. NAJARIAN BY 77/M7M ATTORNEY Oct 9, 1956 H. K. NAJARIANMETHOD OF CONDENSING METALLIC VAPORS CARRIED IN A STREAM OF GAS Originalme March 15, 1952 4 Sheets-Sheet 4 INVENTOR HERAND K. NAJARIAN ATTORNEYUnited States Patent ()filice 2,766,l l4 Patented Oct. 9, 1956 2,786,114METHOD OF CONDENSING METALLIC VAPORS CARRIED IN A STREAM F GA'S HerandK. Najarian, Beaver, Pa., assignor to St. Joseph Lead Company, New York,N. Y., a corporation of New York Original application March 13, 1952,Serial No. 276,330. Divided and this application February 15, 1954,Serial No. 410,108

7 Claims. (Cl. 75 -88) This invention relates to a method forcondensation of metallic vapors, particularly zinc, and represents animprovement in the method disclosed in U. S. Patent 2,070,101, datedFebruary 9, 1937, George F. Weaton and Herand K. Najarian, Condensationof Metallic Vapors.

In the above-mentioned U. S. patent, disclosure is made of a method andapparatus whereby condensation of metallic vapors occurs when metallicvapors arepassed into a mass of molten metal held in an enclosedreceptacle called the condenser. The metallic vapors and accompanyinggases from a reduction furnace bubbling through the mass of molten metalupwardly and forwardly in the upper region of a mass of molten metalcontiguous to the roof portion of the condenser induce flow of moltenmetal concurrently with the bubbling vapor and gases towards the gasoutlet end of the condenser. An equivalent amount of molten metal circulates countercurrently at the lower region of the mass of molten metalcontiguous to the bottom portion of the condenser. One or more bafilesplaced crosswise of the condenser serve to reduce the magnitude ofsurges of metal, and help define the extent of circulation of metalwithin the condenser. Cooling of the molten metal in the condenser, madenecessary by heat given oil? by condensation of metallic vapors toliquid metal and contact of the hot gases with the molten metal, isaccomplished mainly by applying cooling water to the outside steel shellof the condenser. Due to the limited path of circulation of the moltenmetal within the condenser and a low rate of heat transmission throughthe refractory lined shell of the condenser, cooling of the molten metalin the condenser by applying cooling water to the outer steel shell ofthe condenser is not completely satisfactory and the maintenance ofoptimum operation conditions has been difficult.

The present invention relates particularly to an improved method wherebythe flow of molten metal concurrent to the metallic vapors and gases atthe upper region of the molten metal contiguous to the roof of thecondenser is maintained ata maximum, the countercurrent flow at thebottom region of the mass of molten metal is restricted and reduced to aminimum, while a portion of the hotter metal from the condenser near thegas outlet end is diverted to a point outside of the condenser into aseparate receptacle where it is cooled rapidly and eificiently and inlarge volume and is returned to the condenser near the gas inlet endthereof, whereby better cooling and closer control of the temperature ofthe molten metal within the condenser is obtained and a more completecondensation of volatile metals with less blue powder formation resultstogether with a substantial increase in the amount of metal condensedper unit volume of condenser over the apparatus of the prior art.

An object of the invention is to provide a method for condensingmetallic vapors wherein the temperature of the mass of molten metal inthe condenser in continuously maintained at a minimum or preselectedlevel consistent with practical, safe and continuous operation.-

Another object of the invention istoprovide a method for condensingmetallic vapors wherein there is eliminated the destructive effects ofthermal shock to the condenser shell which result when cooling water isapplied over the hot shell after shutdowns for clean-outs, repairs,power failures, etc. In accordance with the present invention, nocooling water need be applied to the condenser shell.

Another object of the invention is to provide a method for condensingmetallic vapors in which maximum concurrent flow of liquid metal,metallic vapors and gases is maintained in the condenser and a highdegree of agitation of the liquid metal is achieved, whereby blue powdersuspended in the liquid metal is converted into coherent liquid metal.

Another object of the invention is to provide a method for condensingmetallic vapors to obtain a larger tonnage of condensed metal per unitvolume of condenser and molten metal held in the condenser than hithertohas been realized.

Another object of the invention is to provide a condenser for condensingmetallic vapors in which progressive thermal expansion of the condenseris minimized.

Another object of the invention is to provide a method for condensingZinc vapors permitting separation of metallic lead from zinc, if such isfound in appreciable quantities admixed with the zinc.

The foregoing and other aims, objects and advantages of the invention asmay be expressed in or be apparent from the following description, areachieved in apparatus for condensing vapors of metals from a stream ofgas carrying the same including a heat insulated entrance chamberconnected to a source of gases and metallic vapors, and exit chamber, areceptacle having its respective ends connected to the chambers andnormally filled with molten metal for a substantial porition of itslength, a suction producing device to draw off gases from the exitchamber and to lift the exposed upper surface of the molten metalsubstantially above its exposed lower surface, an enclosing roof portionto the receptacle in contact with and confining the molten metalintermediate the chambers, bafile means submerged in the liquid metal inthe receptacle to impede and retard the flow of metal from the exitchamber side of the baflle means to the entrance chamber side thereof,means providing a cooling chamber external to and adjacent thereceptacle, first conduit means connecting the receptacle at a pointsubmerged in the metal on the exit chamber side of the bafile means tothe cooling chamber, and second conduit means connecting the coolingchamber to the receptacle at a point submerged in the metal on theentrance chamber side of the baffle means.

The receptacle may take the form of an inclined tubular member and acooling coil may be provided in the cooling chamber.

Where zinc containing appreciable amounts of lead is condensed, a standpipe is provided adjacent the cooling chamber and the latter has a wellconnected to the stand pipe for separation of liquid lead from liquidzinc.

The battle means may have asmall opening adjacent the floor of thecondensing receptacle to provide for limited recirculation of liquidmetal in the receptacle, or it may have no opening at this point.

In its method aspect, the invention comprises condensing vapors ofmetals from a stream of gas carrying the same by passing the gasupwardly through a body of liquid metal confined in a restricted pathbetween a lower free surface of the liquid metal and an upper freesurface of the liquid metal whereby to effect condensation of the metalvapors solely in contact with the liquid metal and with surfacesactively wiped thereby and to effect a generally upward transportationof metal in the restricted path, withdrawing a portion of the metal fromthe upper portion of the restricted path and returning at least aportion of it through a cooling zone external to the restricted'path tothe by utilizing the head created by the upward transportation of metal.

The apparatus of the invention preferably includes an inclined,refractory lined metal tube with upwardly projecting, verticallydisposed, insulated connecting conduits at each end, whereby a mass ofmolten metal is maintained in the inclined tube portion thereof. Suctionis applied to the above assembly through the vertical conduit contiguousto the higher end of the inclined tubular condenser portion. Hot gases,for example from a reduction furnace, comprising metallic vapors andaccompanying gases from which air is excluded, are admitted to thecondenser through the insulated vertically disposed conduit contiguousto the lower end of the inclined tubular condenser portion.

The suction, applied above the level of molten metal at the gasdischarge end, is of such magnitude as to raise and maintain the levelof the upper exposed surface of the molten metal in the inclined tube ata substantial height above the lower exposed surface of molten metal andto depress and maintain the lower surface at a level that permits thevapor and gases to enter the mass of molten metal at a lower exposedsurface.

The metallic vapor and gases are maintained submerged in said mass ofmolten metal by the roof portion of the inclined tubular condenser andtravel upwardly and forwardly in an inclined path through acircumferentially confined mass of molten metal, inducing a flow ofmolten metal concurrent to the vapors and gases bubbling through themass of molten metal. The metallic vapors are condensed to coherentliquid metal by contact with the molten metal and internal surfaces ofthe condenser wiped by the metal, while the uncondensed vapor and gasesescape, after passing through the mass of molten metal, into theconnecting outlet conduit, and thence through suitable conduits to asuction-producing device such as a vacuum pump.

' The heat energy released by the condensation of the vapors of volatilemetals into liquid raises the temperature of the mass of relatively coolmolten metal held in the condenser. To secure continuous efficientcondensation of metallic vapors, it is necessary to extract the heatenergy from the mass of molten metal in the condenser and maintain thetemperature thereof as low as and as near the melting point of the metalas practical operational procedures permit, for reasons more fullyexplained hereinafter. Heretofore cooling of the mass of molten metal inthe condenser has usually been accomplished by applying cooling mediumsuch as water to the outside surface of the refractory lined steel shellof the condenser. However, the low rate of heat transfer through theinside refractory lining of the condenser and the relatively limitedpath of circulation induced within the condenser by bubbling vapors andgases impose definite limitations on the rate of cooling of the mass ofmolten metal in the condenser, making it difiicult to maintain a uniformoptimum temperature level necessary for efficient condensation of vaporsand resulting in excessive blue powder formation and low condensationefficiency.

In accordance with the preferred method of this invention, continuousand efiicient cooling of the mass of molten metal is obtained bycontinuously diverting a portion of the molten metal from the condenserto an outside cooling receptacle through a conduit connected to thecondenser near the gas outlet end, cooling the portion of molten metalwhile it flows through the outside receptacle, and returning at least aportion of the diverted and cooled molten metal back to the condenserthrough a second conduit connecting the outside receptacle to thecondenser near gas inlet end thereof. The outside receptacle,hereinafter called the tapping well, is, in the simplest form, arefractory lined and insulated vessel preferably open on top.

lower portion of the restricted path 7 flows out from the condenser tothe outside tapping well,

through the tapping well, and back to the condenser entirely bygravity-circulation and preferably without the aid of power drivenimpellers, pumps, and the like. The gravity flow of molten metal isinduced by hydraulic head created within the mass of molten metal in"the condenser by air-lift actionof metallic vapors and gasesbubbling inan inclined path upwardly through the molten metal near the roof portionof the condenser, forcing some of the molten metal upwardly towards thegas discharge end of the mass of molten metal, while the return of anequivalent amount of metal through the bottom portion ofthe condenserback towards the lower end of condenser i prevented or substantiallyprevented by baffies positioned crosswise of the condenser and acting asdams. Thus, the level of molten metal at the gas outlet end of thecondenser is raised higher than'the'level otherwise attained solely. bysuction applied thereon. This added height of metal forces a portion ofthe molten metal out through the upper conduit into the tapping welland,'in turn through the second conduit near the lower end of thecondenser, back into the condenser. This flow continues as long assufiicient suction is applied at the upper end of the inclined condensertube to draw vapors and gases through the molten metal.

As the portion of molten metal flows through the tapping well, it iscooled by suitable means, as for instance by natural direct radiationfrom the mass of metal in the tapping well, by cool air circulationaround the tapping well, or, in addition, by having the molten metalcome in contact with cooling surfaces such as a pipe coil carrying waterand immersed in the flowing metal.

The rate of cooling is regulated as for example by varying the extent ofimmersion of the cooling coils in the flowing molten metal, and in turndictated by the desired temperature level in the mass of molten metal inthe condenser .for continuous practical and efficient operation. Forexample, in zinc condensers of the type of the present invention,attached to large electrothermic furnaces and employing the coolingmethod described herein, it is possible to maintain the temperature ofthe molten metal in the condenser at from 475 C. to 525 C. continuously,in which temperature range a very small amount of blue powder is formedand condenser efiiciency is very high. The importance of eiiicientcooling of molten metal in the condenser and maintenance of temperatureat the lowest level possible in practical operation will be seen fromthe following table from which it is apparent that blue powderformation, which is a direct function of theoretical uncondensable zinc,increases sharply as the temperature of the condenser increases, beingvery low at temperatures near the melting point of zinc, for example,only one-half of one per cent at 500 Cf TABLE I Uncondensed zinc vapor,at equilibrium conditions D At 16 in. Hg vacuum (2932 in. Hg barometer)and 45 percent Zn v. per 56 percent noncondensable gas mixture enteringcondenser. I

The outside tapping well communicating with the condenser and permittingimproved cooling of the liquid metal in the condenser furthermoreprovides a simple means whereby excess liquid metal, as it is producedin the condenser by condensation of metallic vapors therein, may bedrawn ofr continuously or intermittently without interfering with thenormal operation of the condenser assembly. The molten metal may bedrawn off from the tapping well continuously through an opening in thewall of the tapping well at the elevation of the liquid metal flowingthrough the tapping well; or, preferably, the metal may be tapped outintermittently by opening a tap hole in the wall of the tapping wellplaced some distance below the level of the liquid metal in the tappingwell. The present method of controlling the temperature of the moltenmetal in the condenser, wherein cooling is obtained principally in thecooperating tapping well attached to the condenser, permits moreadvantageous construction of the condensing receptacle by obviating thenecessity of limiting the thickness of refractory lining and theresilient interlining between the refractory and the steel outside shellof the condenser in order to secure reasonably adequate heat transfercoefficient through the condenser wall. The improved method of coolingof the invention permits the construction of the condenser wall withoutregard to its heat transfer characteristic as an important andcontrolling factor of design, making it possible to use a thickerrefractory lining inside the condenser and to provide more space betweenthe inner refractory lining and the outer steel shell. The enclosing,vacuum tight, steel shell may be filled with resilient material such assheets of mica and asbestos cloth and the like which permits therefractory lining to expand, under continued exposure to heat inside thecondenser, without imposing undue strain on the outside steel shell orthe refractory lining and resulting in a long operating life for theentire condenser assembly.

Improvement in condensing efficiency, realized by the present inventionincreases the over-all capacity of the condenser assembly in terms oftons of zinc produced per day per unit condenser volume upwards ofpercent. For example, on one electrothermic zinc furnace with nominaldaily production capacity of 40 tons of zinc metal, the condenser of thetype shown in the aforementioned Weaton et al. patent of 250 cubic feetwas replaced with a new condenser assembly built according to theprinciples of the present invention and having only 170 cubic feet ofactive condenser volume. The new and smaller condenser handles the samedaily furnace capacity with less blue powder formation, less maintenanceon refractory and steel shell of the condenser, and longer periodsbetween shut-downs for rehabilitation.

The invention will be described with greater particularity withreference to the drawings in which Fig. l is a vertical longitudinalsectional view of one form of zinc condenser embodying the invention;

Fig. 2 is a plan view thereof;

Figs. 3, 4 and 5 are transverse sectional views taken along the lines33, 44 and 5-5, respectively of Fig. 1;

Fig. 6 is a plan view of another form of cooling chamber or tappingwell;

Fig. 7 is a sectional view taken along the line 7-7 of Fig. 6; and

Fig. 8 is a sectional view taken along the line 8-8 of Fig. 6.

Referring to the drawings, particularly to Figs. 1 to 5 thereof, thecondensing apparatus shown is especially adapted for condensing zincvapors, either pure or irnpure, from zinc reduction furnace gases. Thecondensing apparatus has a tubular condensing receptacle 1, inclinedfrom 10 to 45 to the horizontal, preferably inclined 12 to 18 degreesfrom the horizontal, holding a mass of molten metal 2 and having avertically disposed gas inlet conduit 3 communicating with lower end ofthe condensing receptacle and a vertically disposed gas outletconnection 4 at the opposite upper end of the condensing receptacle.Gases from a reduction furnace 5 comprising metallic vapors, such aszinc vapors, and accompanying noncondensable gases such as CO enter thecondensing receptacle or condenser through conduit 3. When sufficientsuction is applied to the mass of molten metal held in the condenserthrough outlet conduit 4 and suction pipe 6 connected to asuction-producing device such as a vacuum pump, not shown, the level ofmolten metal at the upper end of the inclined condenser rises and thesurface thereof is maintained at a substantial height above the lowerexposed surface of molten metal at the lower end of the inclinedcondenser, the lower surface being maintained sufficiently depressed topermit the vapor and gases to enter the mass of molten metal at thelower exposed surface at the lip 7 and bubble upwardly in an inclinedpath through the circumferentially enclosed portion of molten metalcontiguous to the roof portion 8 of the condenser. The vapors and gasesbubble upwardly through the mass of molten metal while thenoncondensable gases pass through the mass of molten metal to the outletconduit and thence through pipe 6 to the vacuum pump, not shown. Theair-lift action produced by the gases bubbling through the portion ofthe body of molten metal adjacent the roof 8 carries forward and upwardpart of the molten metal concurrently with the vapors and gases towardsthe upper exposed surface of the mass of molten metal.

A battle 9 is positioned transversely within the condenser 1 at a pointapproximately mid-way between the ends of the tube. The baflle togetherwith the tube provides a large opening 10 adjacent the roof of the tubeand a very much smaller opening 11 adjacent the floor of the tube. Asecond parallel baffle 12 is positioned in the tube near the gas inletend thereof. This baflle cooperates with the tube to provide an opening13 adjacent the roof that is about the same size as the opening 10 andan opening 14 adjacent the floor that is considerably larger than theopening 11. By virtue of the airlift action of the gases and vaporsbubbling up through the liquid metal, the metal tends to circulate inthe condenser tube 1 in the direction shown by the arrows in Fig. 1.However, the opening 11 is of such a small size as to restrictmaterially the normal tendency of the metal to circulate in the tubeand, in the extreme case, the opening 11 may be dispensed with entirely,the baffle 9 extending to the floor of the tube. For practical reasons asmall opening 11 is desired. It permits limited and restrictedrecirculation of metal eliminating stagnant zones in the condenser,equalizing temperatures, and assisting the condensing action in the roofzone of the tube. Moreover, the hole 11 permits complete drainage of thecondenser through the tap hole 15 when it is desired to shut down theapparatus.

By suitably proportioning the dam or baflle 9 and the opening 11, it ispossible to force the accumulated metal above the dam to flow out of thecondenser through conduit 16 into an associated cooling vessel 17 andfrom there back into the condenser through conduit 18. In the priorcondenser of the aforementioned Weaton et al. patent, it has been founddesirable to use one or more baflles or dams to prevent high amplitudesurging of the large mass of molten metal. That is, the dams served asdamping devices. In effect, the present invention utilizes the dampingenergy to cause the above-described flow of metal.

All parts of the apparatus contacted by liquid metal are refractorylined, suitably by pre-fire shapes of silicon carbide. The open outsidereceptacle 17 serves both as tapping well and as a 'heat transferregion.

Conduit 16 is located near the bottom of the mass of molten metal to:prevent an undue amount of suspended blue powder from passing from thecondenser to the tapping well. The small portion of blue powder whichmay nevertheless =be entrained in the molten metal circulating throughthe vessel 17 comes to the surface of the metal in the tapping well 17and is skimmed from time to time. If molten metal in the condenserintermediate the bafile 9 and the upper exposed surface of the metal isprevented from flowing downwardly, as for instance by closing or greatlyconstricting orifice 11 at the bottom of baffle 9, the molten metalbeing carried upwardly towards the upper exposed surface of the metalflows at a greater rate through conduit 16 to the outside receptacle 17and thence back into the condenser through the conduit 18. Preferredpractice is to make orifice 11 at the bottom of baffle 9 small enough,usually 1 /2 to 2 in diameter, to permit complete draining of moltenmetal from the condenser through an orifice at the lowest place in thecondenser, as for instance at tap hole 15, yet offer sufiicientconstriction to permit substantial fiow of molten metal out of thecondenser to the outside tapping well.

'In the preferred method of cooling the metal in the tapping well, thecooling coil 19, the lower part of which is immersed in molten metalflowing through the tapping well 17, is moved up and down by a hoist,not shown, to vary the extent of cooling surfaces immersed in the moltenmetal, thus controlling the temperature of the flowing molten metal and,in turn, the temperature of the mass of molten metal held in thecondenser.

Liquid metal, as condensed from vapors during operation, preferably isallowed to accumulate in the condenser. Periodically, tap hole 20 on thecooling receptacle 17 is opened and a portion of liquid metal is tappedout and cast into slabs. The condenser may be emptied out completely, asfor instance at the end of a campaign, through bottom tap hole which isnormally closed during the entire campaign.

Vacuum type condensers of large capacity having the preferred coolingapparatus, including an external tapping well with cooling coils andattached to the condensing unit, substantially as described herein, maybe operated for long periods condensing upwards of 40 tons of zinc metalper day from zinc vapor and gases produced in large clectrothermic zincfurnaces. Condenser temperatures in the neighborhood of 500 C. areeasily maintained, at which temperatures very efficient condensation ofzinc vapors from furnace gases is realized.

As an example, a condenser assembly "having a tapping well with acooling coil made of 2-inch pipe carrying cold water at 65 F. receiveszinc vapors and CO gas mixture from an electrothermic zinc furnace. Thecondenser holds a normal charge of approximately 40 tons of molten metaland condenses zinc vapors to metallic zinc at an average daily rate oftons. Temperature of the metal in the condenser is maintained at 500 C.to 525 C.

Zinc metal flows out of the condenser to the tapping well and back intothe condenser :at the rate of approximately 120 tons per hour. Thetemperature of the metal flowing through the tapping well and around thecooling coils drops an average 10 C. to 12 C.

Figures 6, 7 and 8 show in plan and sectional views a modification ofthe outside cooling receptacle whereby, when there is an appreciableamount of metallic lead found in the condensed zinc, the major portionof the metallic lead is separated by settling and separately drawing itoff from a stand-pipe attached to and communicating with the outsidereceptacle. When lead ores smelted in a lead blast furnace contain highpercentages of zinc, practically all the zinc content of the ore,together with small amounts of lead, find their Way into the slag drawnoff the blast furnace. When such slag is smelted further to extract themetallic constituents, as for example in a slag bath electric furnace,the Zinc and lead compounds are volatilized from the slag, and both arereduced to the metallic state as they pass through the bed of overlyingreduction fuel and pass out of the furnace into the zinc condensermainly as metallic vapors. Depending on the lead content of the liquidslag bath in the furnace,

the zinc condensed may carry, for example 1 to 5% metallic lead.

When impure zinc ores or concentrates having appreciable amount of leadare smelted, the gaseous products from the reduction furnace comprisingthe metallic vapors and accompanying non-condensible gases may carrysubstantial amounts of reduced volatile compounds of lead entrained withzinc vapors. Depending on the lead content of such impure zinc ores orconcentrates, the liquid zinc condensed from such gaseous products maycarry appreciable amount of metallic lead, as for example 1 to 5%.

Referring to Figures 6, 7 and 8, a portion of the bottom of the outsidecooling receptacle 17 is depressed to form a well 21. A refractory linedstand-pipe 22 is attached to the outside cooling receptacle 17' by arefractory lined conduit 23, thus connecting the cooling receptacle withthe stand-pipe at or near the bottom of the depressed Well portion ofthe outside cooling receptacle. During operation, metallic lead 24,separating from the molten zinc 25 by gravity, collects at the bottom ofthe well and communicating stand-pipe 22. As metallic lead accumulatesat the bottom of the outside cooling receptacle 17, the level of lead instand-pipe 22 rises somewhat, the level of molten lead in the stand-pipebeing lower than the level of molten zinc flowing through the coolingreceptacle 17 to an extent dependent on the difference in specificgravities of metallic zinc and lead and the height of metallic lead inthe cooling receptacle. In order to prevent molten zinc from finding itsway into the stand-pipe, a suflicient amount of molten lead is pouredinto the assembly at the start of operations, before the priming chargeof molten zinc is filled into the condenser and cooling receptacle.Molten lead is tapped out of the stand-pipe at intervals and as moltenlead accumulates by opening lead tap hole 26.

This application is a division of my application Serial No. 276,330filed March 13, 1952.

I claim:

1. The method of condensing vapors of metals from a stream of gascarrying the same which comprises passing the gas upwardly through abody of liquid metal confined in a restricted path between a lower freesurface of the liquid metal and an upper free surface of the liquidmetal whereby to eifect condensation of the metal vapors solely incontact with mobile surfaces of the liquid metal and with surfacesactively wiped by liquid metal and to effect a generally upwardtransportation of metal in said restricted path, withdrawing a portionof the liquid metal from the upper portion of said restricted path andreturning at least a portion of it through a cooling zone external tosaid path to the lower portion .of the restricted path by utilizing thehead created by said upward transportation.

2. The method of condensing vapors of metals from a stream of gascarrying the same which comprises passing the gas upwardly through abody of liquid metal confined in a restricted path at an angle of from10 to 45 from the horizontal between a lower free surface of the liquidmetal and an upper free surface of the liquid metal whereby to effectcondensation of the metal vapors solely in contact with mobile surfacesof the liquid metal and with surfaces actively wiped by liquid metal andto effect a generally upward transportation of metal in said restrictedpath, withdrawing a portion of the metal from the upper portion of saidrestricted path and returning at least a portion of it through a coolingzone external to said path to the lower portion of the restricted pathby utilizing the head created by said upward transportation.

3. The method of condensing vapors of metals from a stream of gascarrying the same which comprises passing the gas upwardly through abody of liquid metal confined in an inclined restricted path between alower free surface of the liquid metal and an upper free surface of theliquid metal whereby to elfect condensation of the iietal vapors solelyin contact with mobile surfaces of the liquid metal and with surfacesactively wiped by liquid metal and effecting a generally upwardtransportation of liquid metal in said inclined restricted path adjacentthe roof portion thereof and impeding the downward flow of liquid metaladjacent the bottom portion of said inclined restricted path, permittinga portion of said liquid metal from the upper region of said restrictedpath to fiow into a cooling chamber external to said restricted path andthereafter returning cooled liquid metal from said cooling chamber intothe lower region of said liquid metal in said inclined restricted pathby utilizing the head created by said upward transportation.

4. The method of condensing vapors of metals as defined in claim 3,wherein the major cooling of liquid metal in said inclined restrictedpath is effected by continual admixture of relatively cooler liquidmetal flowing from said external cooling chamber into the lower 10region of said body of liquid metal in said restricted path.

5. The method of condensing vapors of metals as defined in claim 3,wherein the temperature of liquid metal in said inclined restricted pathis maintained within a range of about 450-525 C.

6. The method of condensing vapors of metals as defined in claim 3,wherein accumulated condensed metal is drawn oif from said externalcooling chamber.

7. The method of condensing vapors of metals as defined in claim 3,wherein passage of metallic vapors and gases through the body of liquidmetal is induced by suction applied above the upper free surface ofliquid metal in said inclined restricted path.

References Cited in the file of this patent UNITED STATES PATENTS2,478,594 Queneau Aug. 9, 1954

1. THE METHOD OF CONDENSING VAPORS OF METAL FROM A STREAM OF GASCARRYING THE SAME WHICH COMPRISES PASSING THE GAS UPWARDLY THROUGH ABODY OF LIQUID METAL CONFINED IN A RESTRICTED PATH BETWEEN A LOWER FREESURFACE OF THE LIQUID METAL AND AN UPPER FREE SURFACE OF THE LIQUIDMETAL WHEREBY TO EFFECT CONDENSATION OF THE METAL VAPORS SOLELY INCONTACT WITH MOBILE SURFACES OF THE LIQUID METAL AND WITH SURFACESACTIVELY WIPED BY LIQUID METAL AND TO EFFECT A GENERALLY UPWARDTRANSPORTATION OF METAL IN SAID RESTRICTED PATH, WITHDRAWING A PORTIONOF THE LIQUID METAL FROM THE UPPER PORTION OF SAID RESTRICTED PATH ANDRETURNING AT LEAST A PORTION OF IT THROUGH A COOLING ZONE EXTERNAL TOSAID PATH TO THE LOWER PORTION OF THE RESTRICTED PATH BY UTILIZING THEHEAD CREATED BY SAID UPWARD TRANSPORTATION.